Michael Flynn's son is reportedly now a subject in the Russia investigation

Michael Flynn Jr., the son of former national security adviser Michael Flynn, is now a subject in special counsel Robert Mueller’s investigation into whether President Donald Trump’s campaign colluded with Russia during the 2016 election, NBC News reported Wednesday.

The focus on Flynn Jr. has to do in part with work he did for Flynn Intel Group, the lobbying firm he and his father founded after Flynn retired from the military, according to NBC News.

The group has come under increased scrutiny for its ties to Turkey’s increasingly authoritarian president, Recep Tayyip Erdogan, through one of its clients, Kamil Ekim Alptekin.

Flynn was paid $US530,000 as part of his firm’s work for Alptekin, which included efforts to discredit exiled Turkish cleric Fethullah Gulen, who currently resides in Pennsylvania. Erdogan has blamed Gulen for mounting last summer’s failed coup against him and for fomenting dissent within Turkey.

Flynn is under a separate FBI investigation for failing to register as a foreign lobbyist when he provided his services to the Turkish government.

Flynn Jr. appears to have been closely associated with his father’s work. In addition to co-founding and working for Flynn Intel Group, he joined Flynn during a trip to Moscow in December 2015, NBC News reported, during which Flynn was paid $US34,000 to deliver a speech at an event celebrating the state-sponsored news agency RT.

A former business associate of Michael Flynn’s told NBC News that Flynn Jr. had a prominent role in Flynn Intel Group’s day-to-day operations and served as his father’s chief of staff.

The fact that Flynn Jr. was described as a “subject” of Mueller’s investigation indicates that his actions likely lie within the scope of the inquiry, wrote former federal prosecutor Renato Mariotti.

“As a practical matter, what that means is that Mueller is looking at Flynn’s son and he may have some criminal liability,” Mariotti wrote.

However, it could also be that Mueller’s focus on Flynn Jr. is an attempt to coerce his father’s cooperation in the investigation, legal experts have said. This possibility may be especially significant given that Flynn declined a new request on Tuesday to testify before the Senate Intelligence Committee.

Mueller has already employed tactics to compel the cooperation of other key figures in the controversy.

Last month, it was reported that he had teamed up with New York Attorney General Eric Schneiderman as part of his investigation into the business dealings of former Trump campaign chairman Paul Manafort, who is also a subject of the Russia probe.

Mueller’s investigation is focusing on federal crimes, which Trump could exercise his pardon power over. He has no executive authority over state crimes, however, and sources told Politico last month that Mueller working with Schneiderman to probe Manafort’s business dealings was part of an effort to coax him to cooperate with investigators.

Mariotti noted that it was “more likely” that Mueller was zeroing in on Flynn Jr. to prompt his father’s cooperation, which is known as “vicarious cooperation.”

“The idea is that Flynn would cooperate and his son” would benefit, possibly from immunity or a reduced prison sentence, Mariotti said.

Flynn was ousted as national security adviser in February, when it emerged that he had misled Vice President Mike Pence about contacts he’d had with Sergey Kislyak, Russia’s former ambassador to the US, during the transition period.

Flynn ultimately resigned after The Washington Post reported on his conversation with Kislyak.